Gear trains may include a plurality of gears, such as a driving gear, idler gears, and driven gears, used for transferring torque and speed. Gear trains are used in engine applications and, according to a particular engine application, may include a crank gear drivingly coupled with a cam gear through one or more idler gears. The torque and speed transferred from the crank gear to the cam gear may be used for valve opening and closing and for fuel injection. As such, a relatively stiff gear train may be required to maintain proper timing of the cam gear actuated events relative to the engine crank angle. However, dynamic activity of the crank and cam gears during operation of the engine can be substantial and, as a result, may impart significant impulsive torques through the gear train. These impulsive torques may cause gear teeth of adjacent gears to come out of mesh and be rapidly forced back into mesh or cause a backside tooth impact, which can result in excessive noise and can cause premature wear of the gear train components.
Some engineers have sought to address such problems by incorporating dampers, such as pendulum dampers and viscous dampers, into the gear trains. Another approach has been to introduce compliance into the gear train. In general terms, compliant gears provide reduced stiffness, or slack, in the gear train, allowing one or more of the gears to attenuate its response to impulsive loads. Where a particular gear might otherwise be sharply accelerated or decelerated due to a torque impulse, compliance will allow the gear to more gradually adjust its rotation to accommodate the impulsive load. Compliant gears can thus attenuate the impulsive loads, reducing undue wear, mechanical strain, and audible noise.
U.S. Pat. No. 2,992,532 to Miller teaches a control system that uses hydraulic force to actively adjust an idler gear ring axis of rotation. In particular, Miller proposes using a hydraulic system that experiences pressure changes in response to torque fluctuations. As the control system pressure changes, the gear ring axis of rotation is actively shifted. For example, as a result of decreased torque fluctuations over time, the control system pressure decreases to urge the idler gear teeth closer in mesh with the driving gear teeth to reduce occurrences of teeth separation. Thus, Miller teaches a control system for actively shifting a gear ring axis of rotation, rather than a compliant gear system that passively responds to torques exceeding a predetermined threshold. Although various alternatives exist for addressing the negative impacts of dynamic gear train activity, there remains a continuing need for solutions, particularly when previously unrecognized problems are identified.
The present disclosure is directed to one or more of the problems or issues set forth above.